An exponentially averaged Vasyunin formula

We prove a Vasyunin-type formula for an autocorrelation function arising from a Nyman-Beurling criterion generalized to a probabilistic framework. This formula can also be seen as a reciprocity formula for cotangent sums, related to the ones proven in [BC13], [ABB17].Comment: This paper has been written from results already stated in a previous version of another paper in 2018, but has been now submitted separately. arXiv admin note: text overlap with arXiv:1805.0673

On the distribution of a cotangent sum

Maier and Rassias computed the moments and proved a distribution result for the cotangent sum $c_0(a/q):=-\sum_{m<q}\frac mq\cot(\frac{\pi ma}{q})$ on average over $1/2<A_0\leq a/q<A_1<1$, as $q\rightarrow \infty$. We give a simple argument that recovers their results (with stronger error terms) and extends them to the full range $1\leq a<q$. Moreover, we give a density result for $c_0$ and answer a question posed by Maier and Rassias on the growth of the moments of $c_0$.Comment: 10 pages, 2 figure

Period functions and cotangent sums

We investigate the period function of \sum_{n=1}^\infty\sigma_a(n)\e{nz}, showing it can be analytically continued to $|\arg z|<\pi$ and studying its Taylor series. We use these results to give a simple proof of the Voronoi formula and to prove an exact formula for the second moments of the Riemann zeta function. Moreover, we introduce a family of cotangent sums, functions defined over the rationals, that generalize the Dedekind sum and share with it the property of satisfying a reciprocity formula. In particular, we find a reciprocity formula for the Vasyunin sum.Comment: 32 pages, 5 figures, revised version. To appear in Algebra & Number Theor